Packaging pouches are typically made on form, fill and seal machines. For example, using a vertical form, fill and seal machine, a flat web of synthetic thermoplastic film is unwound from a roll and formed into a continuous tube in a tube forming operation, by sealing the longitudinal edges of the film together to form a lap seal or a fin seal. The tube thus formed is pulled vertically downwards to a filling station. The tube is then collapsed across a transverse cross-section of the tube, the position of the cross-section being at a sealing device below the filling station. A transverse heat seal is made by the sealing device at the collapsed portion of the tube, thus making an airtight seal across the tube. The sealing device generally comprises a pair of jaws.
After making the transverse seal, but before the jaws of the sealing device are opened, a quantity of material to be packaged, for example a liquid, is caused to enter the tube at the filling station, and to fill the tube upwardly from the aforementioned transverse seal. The tube is then caused to move downwardly a predetermined distance. This movement may be under the influence of the weight of the material in the tube, or it may be caused by pulling or mechanically driving the tube The jaws of the sealing device are closed again, thus collapsing the tube at a second transverse section. The second transverse section may be above, usually just above the air/material interface in the tube, or the second transverse section may be below the air/material interface. The sealing device seals and severs the tube transversely at the second transverse section. The material filled portion of the tube is now in the form of a pillow shaped pouch. Thus the sealing device has sealed the top of the filled pouch and sealed the bottom of the next pouch to be formed, all in one operation. The filling of the product may be conducted on a continuous or intermittent basis. One such vertical form, fill and seal machine of the type described above is sold under the trade-mark PREPAC. Other suitable machines are sold under the trade-marks INPACO and ELECSTER.
A variety of flowable materials may be packaged in this manner, for example, milk, syrups, sauces, juices, water and the like. The term “flowable material” can include materials that are flowable under gravity or may be pumped. Such materials may include emulsions, pastes, peanut butter, preserves, dough, ground meat, powders, detergents, oils and granular solids. Such pouches can also be used to contain other flowable materials such as foods that are packaged under sterile, pasteurized or aseptic conditions. The packaging conditions will normally require modifications to the machine and also modifications to the methods of packaging.
The pouches produced through this type of process can be manufactured to contain any volume of flowable material. In the situation where drinking fluids are packaged in this fashion, a typical size might be 250 mls or 500 mls. In such instance, it is possible to consume the fluid directly from the pouch. Thus, providing a pouch that includes an easy-open feature for this purpose is desirable especially when served in correctional facilities since it avoids the necessity to use an implement such as a knife or scissors. In addition, since these packages are meant for one-time use and are disposable, it is appropriate that the manner in which they are manufactured is as economical as possible, without sacrificing the basic packaging requirements for the materials in question.
Many solutions have been proposed for producing packages of this type, and typically such packages have included a notch or tear line which allows the package to be opened. For example, French Patent No. 1 216 422 discloses liquid-filled polymer pouches that are produced by collapsing a tube and having an easy-open feature. The easy-open feature comprises a sealed area partially extending across the width of the pouch and a weakened line extending within the sealed area. The weakened line is formed using a set of jaws where one jaw comprises a piano wire.
United Kingdom Patent No. 898,641 discloses a pouch having a line of weakness for easy opening that is produced by pressing the sheet between a solid plate and a ribbed die while heat is applied. The sheet is pinched between the plate and the rib of the die and reduced in thickness but not sheared, or otherwise punctured along the desired line.
U.S. Pat. No. 5,038,550 and European Patent No. 0 372 886 both disclose pouches having a slit formed within a sealed portion. The slit is intended as a device for starting a tear and for directing the tear in a preferred direction. In both cases the sealed portion is formed first using a sealing element and then the slit is formed using a separate cutting operation using a knife.
U.S. Patent Application Publication No. US 2006/0110081 A1 published on May 25, 2006, discloses a pouch for containing a flowable material, provided with an easy-open feature located adjacent to an upper closure or a lower closure of the pouch. The easy-open feature comprises a seal formed between two layers of film and provides a tear line for opening the pouch and tearing a corner off the pouch.
One concern with easy-open features in packaging pouches is that during the production, filling, handling or any manipulation of the pouches, stresses are induced in the film that forms the walls of the pouch. Therefore, depending on the configuration of the easy-open feature, it may produce a stress concentration in the film and hence make the film more susceptible to tearing in specific areas.
Thus there is a need for an improved heat sealing jaw that can be used to easily and economically produce an easy-open feature in a pouch that is sufficiently robust to withstand stresses induced on the pouch during manipulation and/or filling of the pouch.
Accordingly, the present invention provides a heat sealing jaw which can be used to produce a packaging pouch with an easy-open feature, wherein the easy-open feature does not significantly compromise the integrity of the packaging pouch.
According to one aspect, the present invention provides a heat sealing jaw for use in cooperation with an opposing backing jaw for sealing layers of film together to form a sealed portion and a notch within the sealed portion. The heat sealing jaw comprises a jaw body, a heat sealing element secured to the jaw body, a support surface associated with the heat sealing element for clamping the layers of film against the opposing backing jaw and a heat sink coupled to the heat sealing element. The heat sealing element has a sealing face for pressing the layers of film together against the opposing backing jaw and forming the sealed portion. The sealing face has a protrusion for forming the notch within the sealed portion. The heat sink is coupled to the heat sealing element at a location adjacent to the support surface, and during operation, the heat sink induces a temperature gradient along the sealing face of the heat sealing element.
Advantageously, the heat sealing element may further comprise a clamping portion that is disposed at an orientation diverging from a plane along which the layers of film are sealed together. This tends to facilitate the securing of the heat sealing element to the jaw body which may also serve as the heat sink.
According to another aspect, the present invention also provides a heat sealing jaw for use in cooperation with an opposing backing jaw for forming an easy open feature adjacent to an edge of a packaging pouch made from layers of film sealed together. The heat sealing jaw comprises a jaw body, a heat sealing element secured to the jaw body, a support surface associated with the heat sealing element and a heat sink coupled to the heat sealing element. The heat sealing element has a sealing face for forming a sealed portion extending inwardly from the edge of the pouch. Accordingly, the sealing face has an outboard end to be positioned outside of the edge of the pouch, an inboard end to be positioned inside the edge of the pouch and a protrusion for forming the notch within the sealed portion. The support surface is associated with the inboard end of the sealing face for clamping the layers of film against the opposing backing jaw. The heat sink is coupled to the heat sealing element at a location adjacent to the inboard end of the sealing face, and during operation, the heat sink induces a temperature gradient along the sealing face of the heat sealing element.
According to another aspect, the present invention provides a heat sealing element for use in a heat sealing jaw in cooperation with an opposing backing jaw for sealing layers of film together to form a sealed portion and a notch within the sealed portion. The heat sealing element comprises a sealing face for pressing the layers of film together against the opposing backing jaw and forming the sealed portion, and, a clamping portion adjacent to the sealing face. The sealing face has a protrusion for forming the notch within the sealed portion. The clamping portion is disposed at an orientation diverging from a plane along which the layers of film are sealed together.
According to a further aspect, the present invention provides a method of sealing layers of film together to form a sealed portion and a notch within the sealed portion comprising the steps of:                a) providing layers of film to be sealed together between a heat sealing jaw and a cooperating backing jaw, the heat sealing jaw comprising a heat sealing element with a sealing face having a length and a protrusion extending partly along the length of the sealing face;        b) inducing a temperature gradient along the length of the sealing face of the heat sealing element, wherein a first temperature of the sealing face adjacent to the protrusion is higher than a second temperature of the sealing face at a distance from the protrusion;        c) closing the jaws to press the layers of film between the sealing face of the heat sealing element and the backing jaw, and, to simultaneously clamp the film at a location adjacent to the sealing face;        d) holding the jaws closed for a period of time required to form the sealed portion and the notch; and        e) opening the jaws to release the layers of film.        
The above method may be performed on a pouch forming and filling machine such as a vertical form, fill and seal packaging machine, in conjunction with additional steps that are required to form a packaging pouch having an easy-open feature and filled with flowable material. Accordingly, the layers of film may be provided between the heat sealing jaw and the cooperating backing jaw in the form of a film tube that is partially filled with flowable material. The temperature gradient along the length of the sealing face may be induced by extracting heat from the heat sealing element using, for example, a heat sink coupled to the heat sealing element.